Oral Presentation Australian & New Zealand Obesity Society 2014 Annual Scientific Meeting

Are obese children really less fit? Influences of body composition and physical activity on cardiorespiratory fitness in obese and healthy-weight children. (#62)

Margarita D Tsiros 1 , Alison M Coates 1 , Peter RC Howe 2 , Jeff Walkley 3 , Andrew P Hills 4 , Rachel E Wood 5 , Jonathann D Buckley 1
  1. Sansom Institute for Health Research, University of South Australia, Adelaide, SA, Australia
  2. School of Biomedical Sciences & Pharmacy, University of Newcastle, Newcastle, NSW, Australia
  3. School of Health Sciences, RMIT University, Bundoora, Vic, Australia
  4. Mater Research Institute , Mater Mothers’ Hospital, South Brisbane, QLD, Australia
  5. School of Exercise and Nutrition Sciences, Queensland University of Technology, Kelvin Grove, QLD, Australia

Background & Significance: Cardiorespiratory fitness (CRF) is an independent predictor of health outcomes in children and is associated with functional limitations in walking/running capacity in obese youth. Obese children are typically less physically active than their healthy-weight peers and are often assumed to be unfit. This study sought to investigate the relationships between adiposity, physical activity levels and CRF in obese and healthy-weight children. Methods: Obese (N=107) and healthy-weight (N=132) 10-13 year olds participated. Fat-free mass (FFM) and percent fat were assessed by dual energy X-ray absorptiometry. Physical activity was assessed by accelerometry and peak oxygen uptake (VO2peak) by maximal cycle ergometry. VO2peak was corrected for mass and FFM. Mean oxygen uptake during unloaded cycle warm-up was also expressed as a percentage of VO2peak (%UVO2peak). Analyses were adjusted for socioeconomic status (SES) and physical activity (accelerometry). Major Findings: Higher percent fat was inversely associated with VO2peak normalized for mass (r=-0.325, P<0.001) and was positively related to %UVO2 (r=0.426, P<0.001) irrespective of SES and physical activity. Higher percent fat was also inversely associated with VO2peak normalized for FFM (r=-0.249 P<0.001, adjusted for SES), but not after controlling for physical activity (r= -0.096 P=0.158). Concluding statement: Higher adiposity, indicative of obesity, is associated with poorer CRF relative to mass irrespective of physical activity levels. However, low physical activity levels may be responsible for associations between adiposity and CRF relative to FFM, indicating the importance of encouraging physical activity in obese youth.